Does motor training in a mirror box attenuate the loss of motor function following short-term limb immobilization.

Short-term limb immobilization that reduces muscle use for 8–10 hours is known to reduce muscle strength. However, the mechanisms through which this is achieved, and whether these changes can be used to modify motor skill learning, are not known. We have recently shown that unilateral strength training of one limb maintains strength and motor cortical plasticity following short-term immobilization. Interestingly, observation of a motor act performed by oneself, observation of a motor act performed by someone else, and viewing a motor act in a mirror (which is often the case in sport practice) all activate the same neural structures as the actual movement execution, producing subliminal facilitation of neurons forming the motor neural network. The subliminal engagement of neurons might have an adaptive role in motor learning, and therefore action observation seems to be a potential tool to facilitate motor learning during periods of musculoskeletal rehabilitation. A specific form of motor practice that makes use of action observation is mirror training. In mirror training, the practicing limb’s image is superimposed over the resting limb, creating the illusion in the mirror that the resting limb is moving. Mirror training is known to reduce phantom limb pain and enhance recovery of motor function of the paretic lower and upper extremity after a stroke and can also facilitate skill acquisition of the non-trained hand in healthy participants. However, it remains unclear as to whether mirror-training differentially modulates the cross-transfer of strength and motor cortex plasticity following short-term unilateral limb immobilization. Therefore, the purpose of this project is to use a model that combines unilateral limb immobilization and contralateral strength training to determine if strength training of the free limb (with or without a mirror) can attenuate the strength loss acquired during short-term unilateral limb immobilization. These findings have important clinical implications in the management of musculoskeletal or neurological injury that results in limb immobilization.